Hello Tube lovers,
I just receive another lot of our new design with block solder mask PCB. The Dynaco ST-35 Rev 1 PCB that includes the EFB Circuit.
It uses ½ 12AX7A and ½ a 12AU7 per channel. The 12AX7A is a low noise preamplifier that directly drives the cathodes phase splitter 12AU7. We also replaced a single cathode resistor and capacitor with an innovative Enhanced Fixed Bias feature that allows your ST-35 to perform to its full potential with both channels driven. The circuit incorporates once for all a fixed bias operation to enhanced power to its full potential. Audio power will be maintained with both channels driven and distortion will be significantly reduced. The regulator LM237 voltage must be adjusted, and test points are present on the board to connect the VOM and measure 0.27V or 270mV. This is equivalent to have 27mA running on each cathode of EL-84/6BQ5 throughout each 10 Ohms resistor. We are essentially setting up the LM237 to delivery +15VDC when measuring its output in relation to circuit GND. By adjusting the bias, we are averaging the current of four Pentode EL-84/6BQ5. This means one tube can be on 0.28VDC and the other in 0.26VDC, resulting in an average of 0.27VDC. For best performance is recommended to have a well quad matched tube on this project.
Let me know if anyone has questions.
https://www.ebay.com/itm/225774263966?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=wzZzolA2RqW&sssrc=2524149&ssuid=wzZzolA2RqW&widget_ver=artemis&media=COPY
I just receive another lot of our new design with block solder mask PCB. The Dynaco ST-35 Rev 1 PCB that includes the EFB Circuit.
It uses ½ 12AX7A and ½ a 12AU7 per channel. The 12AX7A is a low noise preamplifier that directly drives the cathodes phase splitter 12AU7. We also replaced a single cathode resistor and capacitor with an innovative Enhanced Fixed Bias feature that allows your ST-35 to perform to its full potential with both channels driven. The circuit incorporates once for all a fixed bias operation to enhanced power to its full potential. Audio power will be maintained with both channels driven and distortion will be significantly reduced. The regulator LM237 voltage must be adjusted, and test points are present on the board to connect the VOM and measure 0.27V or 270mV. This is equivalent to have 27mA running on each cathode of EL-84/6BQ5 throughout each 10 Ohms resistor. We are essentially setting up the LM237 to delivery +15VDC when measuring its output in relation to circuit GND. By adjusting the bias, we are averaging the current of four Pentode EL-84/6BQ5. This means one tube can be on 0.28VDC and the other in 0.26VDC, resulting in an average of 0.27VDC. For best performance is recommended to have a well quad matched tube on this project.
Let me know if anyone has questions.
https://www.ebay.com/itm/225774263966?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=wzZzolA2RqW&sssrc=2524149&ssuid=wzZzolA2RqW&widget_ver=artemis&media=COPY